PadMessageHandler.js: fixed logic error in a guard condition

The guard condition on count being non negative and < 100 used the wrong
boolean operator. In its form it was impossible.

This error was introduced in 2013, in 5592c4b0fe.
Fixes #3499

src/node/handler/PadMessageHandler.js

@@ -462,9 +462,9 @@ function handleGetChatMessages(client, message)
 
   var start = message.data.start;
   var end = message.data.end;
-  var count = start - count;
+  var count = end - start;
 
-  if(count < 0 && count > 100)
+  if(count < 0 || count > 100)
   {
     messageLogger.warn("Dropped message, GetChatMessages Message, client requested invalid amout of messages!");
     return;